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18 May 2006

Zombie king suspect alleged to have sent 18 million spams per day

Man arrested in South Korea

Zombie computers are used to send spam and plant unwanted software. Image copyright (c) Sophos
Zombie computers are used to send spam and plant unwanted software.

Experts at SophosLabs™, Sophos's global network of virus, spyware and spam analysis centers, have welcomed the news that the South Korean authorities have arrested a man suspected of running a 16,000-strong network of zombie computers.

According to the state-backed Korea Information Security Agency (KISA), the man is believed to have sent 18 million spam emails to 133 countries every day from his network (or botnet) of compromised computers.

Working with the police, KISA identified a man who has been running the botnet of 16,000 computers for the last six months using it to send out large amounts of loan-related spam.

Last month, Sophos published a report placing South Korea as the third biggest relayer of spam, accounting for almost 10% of all junk mail seen by Sophos's global network of spam traps.

"Spammers usually don't use their own computers to send out their unwanted messages - instead they infect and take over innocent people's vulnerable computers using malware and use them to churn out the spam," said Graham Cluley, senior technology consultant for Sophos. "South Korean computers are often exploited in this way by spammers because of the country's impressive internet infrastructure, but the messages sent from those computers can end up in the inboxes of people anywhere in the world. For the Koreans to catch their first zombie master is great news for everybody who uses the internet."

Zombie computers - are your PCs under someone else's control?

Zombie computers can be used by criminal hackers to launch distributed denial-of-service attacks, spread spam messages or to steal confidential information.

As spammers become more aggressive, collaborating with virus writers to create armies of zombie computers, legitimate organizations with hijacked computers are being identified as a source of spam. This not only harms the organization's reputation, but can also cause the company's email to be blocked by others.

Sophos ZombieAlert™ advises service subscribers when any computer on their network is found to have sent spam to Sophos's extensive global network of spam traps, and provides rapid notification to customers if their Internet Protocol (IP) addresses are listed in public Domain Name Server Block Lists (DNSBL). This information helps customers locate, disinfect, and protect these systems from future attacks.

Sophos continues to recommend that computer users ensure their anti-virus software is up-to-date, and that companies protect themselves with a consolidated solution which can defend them from the threats of viruses, spyware and spam.

About Sophos

More than 100 million users in 150 countries rely on Sophos as the best protection against complex threats and data loss. Sophos is committed to providing complete security solutions that are simple to deploy, manage, and use and that deliver the industry's lowest total cost of ownership. Sophos offers award-winning encryption, endpoint security, web, email, mobile and network security solutions backed by SophosLabs - a global network of threat intelligence centers.

Sophos is headquartered in Boston, US and Oxford, UK. More information is available at